1. Field of the Invention
The present invention relates to intumescent composites and, in particular, to an intumescent firestop device, a method for manufacturing the device, and an intumescent composite for the device.
2. Statement of Related Art
An intumescent firestop device is used to prevent fire from spreading from one room to another through an opening or aperture in a wall, floor, or ceiling through which a pipe runs. A conventional firestop device is wrapped around a pipe (e.g., a PVC plastic pipe) adjacent to the wall (or floor or ceiling) opening. If a fire breaks out in the room, the intumescent material within the firestop device will begin to intumesce (i.e., expand) when the temperature reaches a certain level. The expansion of the intumescent material is directed inward by the outer restraining layer of the firestop device. As a result, the intumescing material crushes the pipe, which is softened by the heat of the fire, and closes off the opening in the wall with a hard char. The resulting hard char must be fire resistant, a thermal insulator, a smoke depressant, and able to withstand the forces exerted by a stream of water from a fire hose.
Many conventional firestop devices require field installation, whereby foil-lined strips of intumescent material are wrapped around a pipe and then a restraining collar is wrapped around the intumescent material and secured by screws or straps. In order to create a cold-gas seal, caulk must be used to fill the annular space between the outside of the firestop device and the opening in the wall.
U.S. Patent No. 4,951,442 (Harbeke, Jr.) discloses a pre-formed firestop collar assembly made of two rigid semi-circular bands that are connected at a hinge line. Each half comprises a rigid restraining layer and two layers of solid intumescent composite. The two layers of solid intumescent composite and the restraining layer must be glued together. Because the intumescent composite is a solid, caulking must still be used to form a cold-gas seal.
In addition, the firestop devices of Harbeke, Jr. require some mechanism, such as foil lining, screws, or metal tabs, to provide heat transfer to ensure that the firestop device starts to intumesce at an appropriate ambient temperature and continues to intumesce at an adequate rate.